Despite being correlated to poor health outcomes, emergency department (ED) overcrowding occurs several times per week in 90% of all EDs in the US. A primary contributor to ED overcrowding is high demand for radiology services (i.e. X-rays), which are relied upon for diagnosis of bone fractures in 7.2 million non-time- sensitive suspected bone fracture patients per year. The total financial impact of this time and resource- consuming task is estimated at more than $1.9 B per year in the US. Ultrasound has been widely investigated as an alternative to X-ray for fracture diagnosis and assessment of treatment (i.e. fracture reduction) in the ED; however, conventional ultrasound image quality of bone anatomy is poor, has a limited field of view, and is challenging to interpret. This Phase I SBIR proposal seeks funding to test the feasibility of a portable ultrasound-based 3D bone imaging device, referred to as the FractureFinder, for diagnosis of bone fractures in the ED. Key technological innovations of this project include a new conformable, piston-array-based 3D imaging transducer that is technologically advanced over conventional ultrasound due to: reduced bone imaging artifact, increased field of view, and conformability to the shape of the patient's skin surface. Additionally, an advanced bone imaging sequence and reconstruction method is introduced that enhances delineation of bone surfaces. The long-term goal of this project is to create a compact, portable ultrasound-based 3D bone imaging system with sensitivity and specificity for bone fractures equivalent to that of digital X-ray. The Phase I hypothesis is that an ultrasound-based 3D bone imaging device can be fabricated to achieve equivalent fracture detection performance to X-ray in an ex vivo porcine tibia-fibula fracture model. A functional handheld ultrasound prototype incorporating a conformable transducer with dimensions < 25 cm x 20 cm x 6 cm will be fabricated. Bone imaging reconstruction techniques will be developed in simulation to achieve resolution <= 200 m with sensitivity > 99% over bone angles spanning 100. The imaging techniques and reconstruction algorithms will be implemented on the prototype and tested in an ex vivo whole porcine tibia- fibula model. Research plans for Phase II include a refined prototype with industrial design and graphic user interface development for the purposes of conducting an in vivo pilot study at the University of Virginia Hospital. The proposed 3D bone imaging device is expected to speed diagnosis of bone fractures in the ED, allowing faster treatment and patient discharge without using valuable radiology resources. It is estimated that the device could save at least 6.3 million ED hours and $1.16 B to the healthcare system, annually. The fully saturated US emergency medicine market for the FractureFinder is estimated at $120 M in revenues per year. Additional applications for the product include rural healthcare, sports medicine, battlefield, and orthopedic, the latter of which has an estimated fully saturated US market of $209 M/yr.